This invention relates generally to medical mammography systems that are designed to detect non-palpable lesions of the female breast. More particularly, this invention is directed to an advanced mammographic needle biopsy system for quickly and easily localizing difficult non-palpable lesions to obtain cell or tissue samples. A surgical biopsy performed because a mammography shows a suspected malignant lesion leads, in many cases, to extensive disfiguring surgery of the breast. This occurs despite the fact that the pathology conducted after the surgery in most cases reveals that there is no sign of cancer. Surgical biopsies of this sort are costly, involved, and tie up surgical resources for which there is often a greater need elsewhere.
A known diagnostic system for detecting breast cancer is the TRC Mammotest system manufactured by Tekniska Roontgencentralen AB of Sweden. This prior art system functions in accordance with the principle that a tumor which is photographed by X-ray from separate angles relative to the normal of the film plane is projected in different positions on the film. The X-Y coordinates for these projections can then be measured in relation to a pair of X-Y coordinate scales that are projected onto the film as the X-rays are being taken. The position of the tumor can be calculated using known geometric relationships. A puncture instrument is then used to precisely insert a biopsy needle into the breast until the tip of the needle is located at the center of the tumor.
During operation of the prior art TRC Mammotest system, the patient is in a recumbent prone position on a table that can be raised or lowered, the breast protuding pendulant through an aperture at the cranial end of the table. A compression plate holds the breast firmly in a suitable projection against an X-ray film holder. It is advantageous in several respects that the patient be in a prone position during the examination, rather than standing or sitting, as is the case in conventional mammography screening systems. First, this position, in which the breast is pendulant, makes positioning the breast much easier. In addition, the prone position allows even small breasts to be compressed satisfactorily for mammography and subsequent biopsy. As the patient should not be allowed to move the breast during the procedure, this condition can be achieved much easier if she is in a recumbent prone position. Finally, it is also desirable from a safety point of view that the procedure be conducted while the patient is in a prone position, as there is always a risk of fainting in any type of surgical examination.
Two X-ray views of the compressed breast are conventionally taken, at angles of +15 degrees and -15 degrees to the normal through the plane of the film. This technique results in two different projections of the lesion in relation to a pair of radio opaque orthogonal coordinate scales that are engraved into the compression plate and are thus projected onto the X-ray film. A point of interest appearing on the two X-ray views is selected, and a manual measurement of the X and Y coordinates of the point is made with reference to the pair of orthogonal coordinate scales appearing on the two X-ray views. These manually measured X and Y coordinates are then manually entered into a calculator for calculation of the composite coordinates used for manually setting the puncture instrument. The puncture instrument, fitted with a desired biopsy needle, is then placed in a position agreeing with the calculated composite coordinates of the point of interest and the needle is inserted into the breast until the tip of the needle reaches the point of interest. As a check, and to provide a documented record that the biopsy sample has been taken from the intended point of interest within the breast, two additional X-ray views are taken while the needle is inserted in the breast. The biopsy needle is then withdrawn and the sampling terminated.
The prior art system described above is disadvantageous in several respects. For instance, the table on which the patient lies during the procedure, while it can be lowered to permit mounting by the patient and then raised to give the doctor room beneath the table to conduct the procedure, is nevertheless fixed in a horizontal position. Since the table does not fold and cannot be inclined from its fixed horizontal position, it is oftentimes difficult for patients to mount the table, even in its lowered position. It is also a disadvantage that the aperture through which the breast under examination depends is of a fixed size in that it is therefore difficult to accommodate a wide range of women's sizes. In addition, the table of the prior art system is strictly flat, thereby preventing examination of a patient's breast tissue that lies very near the chest wall. Also, accuracy and speed of the prior art system are impaired as a result of the required manual measurement, with reference to the projected coordinate scales, of the X and Y coordinates of the point of interest displayed on the two X-ray views. Moreover, the X and Y coordinate scales that are projected onto the film as the X-rays are being taken result in obscuring a portion of the breast tissue that would otherwise be clearly shown in the X-ray views.
It is therefore an object of the present invention to provide an improved mammographic needle biopsy system in which the table on which the patient lies during the examination procedure has a hinged foot section that permits easy mounting and dismounting by the patient.
It is a further object of the present invention to provide an improved mammographic needle biopsy system in which the table on which the patient lies during the examination procedure is concave with respect to its longitudinal axis to permit examination of the patient's breast tissue that is adjacent the chest wall.
It is a further object of the present invention to provide an improved mammographic needle biopsy system in which a breast aperture in the surface of the table on which the patient lies during the examination procedure includes an adjustable diaphragm for partially covering a selected portion of the breast aperture to thereby permit exposure of only the breast under examination.
It is a further object of the present invention to provide an improved mammographic needle biopsy system in which the patient's breast is held in a compressed position in a spaced apart relationship between an X-ray film and an X-ray beam source to result in magnification of X-ray images of the breast.
It is a further object of the present invention to provide an improved mammographic needle biopsy system in which radially pivoting film and X-ray arms are supported by means of tapered roller bearings and in which those arms are locked in a desired position by means of wedge-shaped mating locking parts to prevent undesirable movement of the arms and resultant loss of overall accuracy of the measurements made by the system.
It is a further object of the present invention to provide an improved mammographic needle biopsy system in which a biopsy needle is positioned in the same plane as that containing the horizontal pivoting axis of a puncture instrument holding the biopsy needle.
It is a further object of the present invention to provide an improved mammographic needle biopsy system in which a spring-loaded biopsy gun is employed for rapid insertion of a biopsy needle to a specific point of interest within the patient's breast.
It is a further object of the present invention to provide an improved mammographic needle biopsy system in which a digitizer is employed to digitize the location of a point of interest within the patient's breast that appears on a pair of stereo X-rays that do not have coordinate scales depicted thereon and in which the vertical angle, horizontal angle, and insertion depth parameters defining that point of interest are automatically calculated and displayed to the user.
It is a further object of the present invention to provide an improved mammographic needle biopsy system in which micrometers and a depth stop controlling a puncture instrument for adjusting the vertical angle, horizontal angle, and insertion depth parameters of a biopsy needle held by the puncture instrument include position encoders and motorized means for automatically setting those parameters in response to a digitized determination of the values of those parameters associated with a specific point of interest within the patient's breast.